This invention relates generally to a computer tomograph (CT) imaging system and more particularly to a CT detector module and reflector useful therewith and to methods for preparing and using the detector module and reflector.
In at least one known computed tomography (CT) imaging system configuration, an x-ray source projects a fan-shaped beam which is collimated to lie within an X-Y plane of a Cartesian coordinate system and generally referred to as the “imaging plane”. The x-ray beam passes through the object being imaged, such as a patient. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is dependent upon the attenuation of the x-ray beam by the object. Each detector element of the array produces a separate electrical signal that is a measurement of the beam attenuation at the detector location. The attenuation measurements from all the detectors are acquired separately to produce a transmission profile.
In known third generation CT systems, the x-ray source and the detector array are rotated with a gantry within the imaging plane and around the object to be imaged so that the angle at which the x-ray beam intersects the object constantly changes. A group of x-ray attenuation measurements, i.e., projection data, from the detector array at one gantry angle is referred to as a “view”. A “scan” of the object comprises a set of views made at different gantry angles, or view angles, during one revolution of the x-ray source and detector. In an axial scan, the projection data is processed to construct an image that corresponds to a two-dimensional slice taken through the object. One method for reconstructing an image from a set of projection data is referred to in the art as the filtered back projection technique. This process converts the attenuation measurements from a scan into integers called “CT numbers” or “Hounsfield units”, which are used to control the brightness of a corresponding pixel on a cathode ray tube display.
At least one known detector in CT imaging systems comprises a plurality of detector modules, each having a scintillator array optically coupled to a semiconductor photodiode array that detects light output by the scintillator array. The scintillator array in at least one known CT detector is produced with individual diced scintillator elements with the gap between scintillators elements filled with a reflector material applied through a casting operation. This cast reflector is made of a two part epoxy and a chrome pigment used in one known typical CT semiconductor photodiode detector array. Such cast reflectors are sometimes damaged by X-ray exposure which causes color center formation, reduces reflectivity and causes lower light output from each photodiode detector cell. Cast reflectors are protected by tungsten wires and plates in known CT systems and have a certain thickness to sufficiently reduce cross talk. Cast reflectors are typically produced in a casting process whereby the scintillator array and epoxy is cast in molds.
Accordingly it would be desirable to provide an improved reflector which is comparatively less susceptible to radiation damage, offers enhanced resistance to color center formation and thereby provides improved light collection efficiency along with potentially lower cross talk.